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Rewrite write_leb_i64 (fixes bug with upper bits of constant)

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Fabian 2021-04-17 18:23:29 -05:00
parent 2f2fff26a9
commit ffac529747
1 changed files with 13 additions and 20 deletions
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33
src/rust/leb.rs
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@ -2,34 +2,27 @@ pub fn write_leb_i32(buf: &mut Vec<u8>, v: i32) { write_leb_i64(buf, v as i64);
pub fn write_leb_i64(buf: &mut Vec<u8>, mut v: i64) {
// https://en.wikipedia.org/wiki/LEB128#Encode_signed_integer
// http://llvm.org/doxygen/LEB128_8h_source.html#l00048
let mut more = true;
let negative = v < 0;
let size = 32;
while more {
let mut byte = (v & 0b1111111) as u8; // get last 7 bits
v >>= 7; // shift them away from the value
if negative {
v |= (!0 as i64) << (size - 7); // extend sign
}
let sign_bit = byte & (1 << 6);
if (v == 0 && sign_bit == 0) || (v == -1 && sign_bit != 0) {
more = false;
}
else {
byte |= 0b10000000; // turn on MSB
loop {
let mut byte = v as u8 & 0b0111_1111;
v >>= 7;
let sign = byte & (1 << 6);
let done = v == 0 && sign == 0 || v == -1 && sign != 0;
if !done {
byte |= 0b1000_0000;
}
buf.push(byte);
if done {
break;
}
}
}
pub fn write_leb_u32(buf: &mut Vec<u8>, mut v: u32) {
loop {
let mut byte = v as u8 & 0b01111111; // get last 7 bits
v >>= 7; // shift them away from the value
let mut byte = v as u8 & 0b0111_1111;
v >>= 7;
if v != 0 {
byte |= 0b10000000; // turn on MSB
byte |= 0b1000_0000;
}
buf.push(byte);
if v == 0 {